The goals of this project are to assess the expression and function of membrane molecules on immune cells and to characterize viral antigens which are targets of the immune response. The research is focused on immune reactivity to measles virus and human T cell lymphocytotropic virus I (HTLV-I). immune responses to the individual components of these viruses are being examined in patients with neurological diseases. Antibodies in the blood and the CSF are measured by ELISA. Cellular immune responses are determined by lymphocyte proliferation and cytotoxicity. Purified viral proteins are prepared by procedures developed in our laboratory and used in these studies. The expression of various molecules on the outer membrane surface is assessed on lymphocytes from patients with neurological disorders. This research is currently focused on HTLV-I-associated myelopathy/tropical spastic paraplegia, (HAM/TSP) a chronic neurological disease associated with HTLV-I, but parallel studies are also being conducted in other disorders. The expression of HTLV-I genome in lymphocytes from patients with HAM/TSP, normal carriers of HTLV-I, and multiple sclerosis is being evaluated. The effect of HTLV-I infection on immune function is being studied.